Add the ksyms(4) pseudo driver. The ksyms driver allows a process to

get a quick snapshot of the kernel's symbol table including the symbols
from any loaded modules (the symbols are all merged into one symbol
table).  Unlike like other implementations, this ksyms driver maps
memory in the process memory space to store the snapshot at the time
/dev/ksyms is opened.  It also checks to see if the process has already
a snapshot open and won't allow it to open /dev/ksyms it again until it
closes first.  This prevents kernel and process memory from being
exhausted.  Note that /dev/ksyms is used by the lockstat(1) command.

Reviewed by:	gallatin kib (freebsd-arch)
Approved by:	gnn (mentor)

3 files changed, 78 insertions, 0 deletions

diff --git a/sys/kern/link_elf.c b/sys/kern/link_elf.c
index c17dd15..5ab1ce5 100644
--- a/sys/kern/link_elf.c
+++ b/sys/kern/link_elf.c
@@ -137,6 +137,8 @@ static int	link_elf_each_function_nameval(linker_file_t,
 				linker_function_nameval_callback_t,
 				void *);
 static void	link_elf_reloc_local(linker_file_t);
+static long	link_elf_symtab_get(linker_file_t, const Elf_Sym **);
+static long	link_elf_strtab_get(linker_file_t, caddr_t *);
 static Elf_Addr	elf_lookup(linker_file_t lf, Elf_Size symidx, int deps);
 
 static kobj_method_t link_elf_methods[] = {
@@ -151,6 +153,8 @@ static kobj_method_t link_elf_methods[] = {
     KOBJMETHOD(linker_each_function_name, link_elf_each_function_name),
     KOBJMETHOD(linker_each_function_nameval, link_elf_each_function_nameval),
     KOBJMETHOD(linker_ctf_get,          link_elf_ctf_get),
+    KOBJMETHOD(linker_symtab_get, 	link_elf_symtab_get),
+    KOBJMETHOD(linker_strtab_get, 	link_elf_strtab_get),
     { 0, 0 }
 };
 
@@ -1390,3 +1394,29 @@ link_elf_reloc_local(linker_file_t lf)
 	}
     }
 }
+
+static long
+link_elf_symtab_get(linker_file_t lf, const Elf_Sym **symtab)
+{
+    elf_file_t ef = (elf_file_t)lf;
+    
+    *symtab = ef->ddbsymtab;
+    
+    if (*symtab == NULL)
+        return (0);
+
+    return (ef->ddbsymcnt);
+}
+    
+static long
+link_elf_strtab_get(linker_file_t lf, caddr_t *strtab)
+{
+    elf_file_t ef = (elf_file_t)lf;
+
+    *strtab = ef->ddbstrtab;
+
+    if (*strtab == NULL)
+        return (0);
+
+    return (ef->ddbstrcnt);
+}
diff --git a/sys/kern/link_elf_obj.c b/sys/kern/link_elf_obj.c
index 7734745..60c89d6 100644
--- a/sys/kern/link_elf_obj.c
+++ b/sys/kern/link_elf_obj.c
@@ -140,6 +140,8 @@ static int	link_elf_each_function_nameval(linker_file_t,
 				linker_function_nameval_callback_t,
 				void *);
 static void	link_elf_reloc_local(linker_file_t);
+static long	link_elf_symtab_get(linker_file_t, Elf_Sym **);
+static long	link_elf_strtab_get(linker_file_t, caddr_t *);
 
 static Elf_Addr elf_obj_lookup(linker_file_t lf, Elf_Size symidx, int deps);
 
@@ -155,6 +157,8 @@ static kobj_method_t link_elf_methods[] = {
 	KOBJMETHOD(linker_each_function_name,	link_elf_each_function_name),
 	KOBJMETHOD(linker_each_function_nameval, link_elf_each_function_nameval),
 	KOBJMETHOD(linker_ctf_get,		link_elf_ctf_get),
+	KOBJMETHOD(linker_symtab_get, 		link_elf_symtab_get),
+	KOBJMETHOD(linker_strtab_get, 		link_elf_strtab_get),
 	{ 0, 0 }
 };
 
@@ -1286,3 +1290,29 @@ link_elf_reloc_local(linker_file_t lf)
 		}
 	}
 }
+
+static long
+link_elf_symtab_get(linker_file_t lf, Elf_Sym **symtab)
+{
+    elf_file_t ef = (elf_file_t)lf;
+    
+    *symtab = ef->ddbsymtab;
+    
+    if (*symtab == NULL)
+        return (0);
+
+    return (ef->ddbsymcnt);
+}
+    
+static long
+link_elf_strtab_get(linker_file_t lf, caddr_t *strtab)
+{
+    elf_file_t ef = (elf_file_t)lf;
+
+    *strtab = ef->ddbstrtab;
+
+    if (*strtab == NULL)
+        return (0);
+
+    return (ef->ddbstrcnt);
+}
diff --git a/sys/kern/linker_if.m b/sys/kern/linker_if.m
index aadcf04..379bc0e 100644
--- a/sys/kern/linker_if.m
+++ b/sys/kern/linker_if.m
@@ -105,6 +105,24 @@ METHOD int ctf_get {
 };
 
 #
+# Get the symbol table, returning it in **symtab.  Return the 
+# number of symbols, otherwise zero.
+#
+METHOD long symtab_get {
+	linker_file_t	file;
+	Elf_Sym		**symtab;
+};
+
+#
+# Get the string table, returning it in *strtab.  Return the
+# size (in bytes) of the string table, otherwise zero.
+#
+METHOD long strtab_get {
+	linker_file_t	file;
+	caddr_t		*strtab;
+};
+
+#
 # Load a file, returning the new linker_file_t in *result.  If
 # the class does not recognise the file type, zero should be
 # returned, without modifying *result.  If the file is